The most common source of energy during modern times has been fossil fuels, such as coal, oil and natural gas. In recent years, the rapid expansion of the world's population coupled with accelerated technological development of large sectors of the world has produced a dramatic increase in the demand for energy. As a result, fossil fuels are being used much faster than they can be obtained and this imbalance can only worsen if we continue to rely solely on these fuels for our energy needs. Thus, there is an urgent need for developing other sources of energy. One alternate energy source currently receiving a great deal of attention is that of solar energy. An overriding problem in the harnessing of solar energy is that the environment of the solar steam generating and superheating unit exposes it to considerable transients of thermal loading due to diurnal cycles and cloud shadowing. Thus, a solar steam generating and superheating unit may find itself exposed to maximum heat flux in a localized area with essentially no heat flux in many of its other heat absorbing areas due to cloud shadowing. This condition gives rise to excessive thermal stresses with eventual failure of the affected heat transfer surfaces. The prior art has sought to alleviate this problem at the expense of high pressure losses, by requiring extremely high fluid flows through the tubes associated with the heat transfer surfaces; or by increasing the size of the solar steam generating and superheating unit. The present invention seeks to eliminate these economically unattractive alternatives of the prior art.